ASM-Hackathon

Transcript

1. Reverse Engineering of Al 6061 Heat Treatment ASM-GT Materials Data Challenge David Freiberg, Christine Palmer, Axel-Jose Munoz The Iron Dragons
2. Our company wants to redesign aircraft parts that were built in the 1950- 1960 timeframe. Unfortunately the original company doesn’t exist anymore and some of the data for Al 6061 was lost. • Al 6061 undergoes a heat treatment to obtain certain mechanical properties and to age the metal. • We have EBSD, TEM, SEM, and Optical data from Al 6061 treated at 400℉, 650℉, and 775℉. • Find the temperature at which the metal was treated at. • We could “purchase” EBSD, TEM, SEM, and Optical data of the metal in question. We could also hire consultants for a fee for assistance on the project. Problem Introduction | 2
3. Material Specifications Aluminum (Al 6061 T651 Temper) Silicon (0.4% - 0.8%) Iron (< 0.7%) Copper (0.15% - 0.4%) Manganese (< 0.15%) Magnesium (0.8% - 1.2%) Chromium (0.04% - 0.35%) Zinc (< 0.25%) Titanium (< 0.15%) Other elements (< 0.05% each, < 0.15% total) Remainder aluminium (95.85–98.56%) Materials Specifications | 3 Phase Size (nm) Description β’-Mg2Si / Mg5Si6 9.31 to 15.1 Needle / rod shaped (Fe,Mn,Cr)3SiAl12 91.5 to 145 Ill shaped cuboidal or irregular shaped Al9Fe2Si2 120 Elliptical shaped Heat Treatments 6061 T651 400°F 2 hours 6061 T651 650°F 2 hours 6061 T651 775°F 2 hours
4. Background: Precipitation Hardening • Precipitation in Alloy System: • Nucleation of precipitate clusters in Al 6061 is dependent on the Gibbs free energy of the system • The probability (P) of a thermodynamic fluctuation of critical free energy, ∆G*, and the jump frequency of growth species, Γ, from one site to another are given by: • Rate of nucleation is then given by: Background | 4
5. Background: Precipitation Hardening Background | 5 Transition Points 1. Partial transformation of β’ precipitate (needle shaped to rod shaped): 572°F 2. Nose (Fastest Transformation): 707°F 3. Total Transformation (needle shaped to rod shaped): 752°F
6. Optical Micrographs (x25) SECTION TITLE | 2 Filtered Images | 6 400℉ 650℉ 775℉ As Received Mystery Heat
7. Particle Size Analysis SECTION TITLE | 2 Filtered Images | 7 400℉ - 20x Unknown - 20x 650℉ - 20x The distributions changed dramatically at 650℉, but there was no readily discernible difference between the 400℉ sample and the unknown sample. This is due in part to the sudden nucleation of precipitates as the heat treatment temperature approaches 707℉, the “nose” of the β’ transformation curve.
8. Fast Fourier Transformations FFT | 8 Particulate Directionality 400℉ - 5x Fast Fourier Transform 400℉ - 5x
9. Particulate Count Particulates | 9 20x 50x 100x 400℉ Unknown 650℉
10. Particulate Count Particulates | 10 Only the smallest particles will represent the particulate clusters in the β’ phase. As the rate of nucleation below the nose of the TTT curve is proportional to Gibbs Free Energy, an exponential function, the temperature was determined via a logarithmic interpolation of particulate count between 400 ℉ and 650 ℉. The estimated heat treatment from this interpolation was ~520℉. Interpolated Heat Treatment Temperature vs. Particle Size
11. To obtain the heat treatment temperature of the metal, we used three different processes: • Fast Fourier Transformation (FFT) ◦ Applicable between temperatures 650℉ - 775℉ due to the phase transition. • Particle Count ◦ Applicable between temperatures 650℉ - 775℉. • Particulate Count ◦ Applicable between temperatures 400℉ - 650℉ due to precipitate nucleation. To distinguish between the two temperature regions we visually estimated the number of rod shaped particulates. The unknown sample was between 400℉ - 650℉, so we used particulate count. The estimated heat treatment temperature of the metal is approximately 520℉. The data for this experiment can be found at: https://drive.google.com/folderview? id=0BxjfpZa9juuwcGdGc0FadkFWdUU&usp=sharing Conclusion Conclusion | 11
12. Budget Budget | 12 Item Quantity Cost Optical Micrograph 5 $10/ea Consulting Fee (Khosravani) 1 $20 TOTAL: $70
13. QUESTIONS? Budget | 12